CN111293326A

CN111293326A - Separator assembly for fuel cell and fuel cell stack including the same

Info

Publication number: CN111293326A
Application number: CN201910338647.8A
Authority: CN
Inventors: 许诚日; 梁酉彰; 郑柄宪
Original assignee: Hyundai Motor Co; Kia Motors Corp
Current assignee: Hyundai Motor Co; Kia Corp
Priority date: 2018-12-06
Filing date: 2019-04-25
Publication date: 2020-06-16
Also published as: JP2020092076A; US11658313B2; KR20200069452A; JP7236913B2; US20200185730A1; DE102019207234A1

Abstract

The present invention provides a separator assembly for a fuel cell, comprising: a first separator having a protruding sealing protrusion providing a seal; a second separator joined to the first separator to be integrated therewith and having an arch-shaped protrusion protruding in the same direction as the sealing protrusion at a position corresponding to a position where the sealing protrusion is formed; a spacer provided on a concave surface of the projection opposite to a convex surface of the projection at a position where the projection of the second separator is formed; and a sealant applied to a convex surface of the sealing convex portion at a position where the sealing convex portion of the first separator is formed.

Description

Separator assembly for fuel cell and fuel cell stack including the same

Technical Field

The present invention relates to a separator assembly for a fuel cell and a fuel cell stack including the same, and more particularly, to a fuel cell stack configured to have improved airtightness and durability while reducing production costs.

Background

As is well known in the art, a fuel cell is a power generation device that converts chemical energy of fuel into electrical energy through an electrochemical reaction in a stack. Fuel cells have a wide range of applications, including use as industrial power generation devices, use as household power generation devices, power vehicles, and power small electronic devices such as portable devices. In recent years, fuel cells are increasingly used as efficient clean energy sources.

Fig. 1 (prior art) is a view showing the structure of a typical fuel cell stack, fig. 2 (prior art) is a view showing a unit cell of a fuel cell to which a subgasket (subgasket) is applied, and fig. 3 (prior art) is a view showing the arrangement of gaskets in the unit cell of the fuel cell to which the subgasket is applied.

As shown in fig. 1, a typical fuel cell stack has a Membrane Electrode Assembly (MEA)10 located at the innermost portion thereof. The MEA 10 includes a Polymer Electrolyte Membrane (PEM)11 that allows positively charged ions (protons) to migrate therethrough, and Catalyst Layers (CL), i.e., an anode 12 and a cathode 13, coated on both sides of the PEM 11 to cause a reaction of hydrogen and oxygen.

Further, a Gas Diffusion Layer (GDL)20 is laminated on the outer side of the MEA 10, i.e., the outer side where the anode 12 and the cathode 13 are located, and

separators

30a and 30b, each having a flow field for supplying fuel and discharging water generated by reaction in the MEA 10, are respectively located on the outer sides of the GDL 20 with a gasket 40 interposed between the

separators

30a and 30 b. End plates 50 are assembled to the outermost sides of the MEA 10 to structurally support and secure the various components described above in place.

Thus, at the anode 12 of the fuel cell stack, an oxidation reaction in which hydrogen is oxidized occurs to generate hydrogen ions (protons) and electrons, and the generated protons and electrons flow to the cathode 13 through the PEM 11 and the wire, respectively. At the cathode 13, water is produced by an electrochemical reaction involving protons and electrons flowing out from the anode 12, and oxygen contained in the air, and the flow of electrons generates electric power.

Meanwhile, the

separators

30a and 30b are generally manufactured such that bosses (lands) serving as supports and channels serving as flow paths of the fluid are alternately repeated.

In other words, a typical separator has a structure in which lands and channels (flow paths) are alternately repeated in a serpentine configuration. Therefore, the channel of one side of the separator facing the GDL 20 serves as a space through which a reaction gas such as hydrogen or air flows, and the channel of the other side serves as a space through which a coolant flows. Thus, a single unit cell may be composed of a pair of separators, i.e., one separator with a hydrogen/coolant channel and the other separator with an air/coolant channel.

On the other hand, as shown in fig. 2, the MEA 10 includes a subgasket 14 at the peripheral portion around the anode 12 and cathode 13 to facilitate handling of the PEM 11, anode 12 and cathode 13 while improving the gas tightness of the stack.

Further, a plurality of inlet manifolds and outlet manifolds are provided on both sides of the subgasket 14 and both sides of the

separators

30a and 30b, respectively.

On the other hand, as shown in fig. 3, since the reaction gas and the coolant must flow between the sub-gasket 14 and the pair of

separators

30a and 30b, injection-molded

rubber gaskets

40a, 40b, and 40c having a predetermined thickness are arranged between the sub-gasket 14 and the pair of

separators

30a and 30 b. Therefore, when the unit cells are stacked one on another, the gaskets are compressed, thereby ensuring the airtightness of the cell stack while maintaining the interval therebetween.

However, the

rubber pads

40a, 40b, and 40c are expensive to manufacture. Therefore, a separator having a sealing protrusion (bead seal) is proposed. Sealing protrusions having a height equal to the thickness of the

gaskets

40a, 40b and 40c disposed between the separators integrally protrude from the surfaces of the separators, and a sealant is applied to the separators in the form of a thin layer, thereby ensuring the airtightness of the cell stack.

However, in the case where a fuel cell stack is formed by stacking a plurality of unit cells on each other and then pressing them, the shape of the sealing convex portion is changed due to the surface pressure acting on the portion where the sealing convex portion is formed, resulting in a decrease in the airtightness of the stack.

The foregoing is intended only to aid in understanding the background of the invention and is not intended to represent that the invention falls within the scope of the relevant art as known to those skilled in the art.

Disclosure of Invention

Accordingly, the present invention provides a fuel cell and a fuel cell stack including the same, wherein the fuel cell stack is configured to have improved airtightness and durability while reducing production costs.

According to an aspect of the present invention, there is provided a separator assembly for a fuel cell, the separator assembly comprising: a first separator having a protruding sealing land (bead seal) providing a seal; a second separator joined to the first separator to be integrated therewith and having an arch-shaped protrusion protruding in the same direction as the sealing protrusion at a position corresponding to a position where the sealing protrusion is formed; a gasket (gasket) provided on a concave surface of the protrusion opposite to a convex surface of the protrusion at a position where the protrusion of the second separator is formed; and a sealant applied to a convex surface of the sealing convex portion at a position where the sealing convex portion of the first separator is formed.

The protrusion height of the protrusion formed at the second separator may be lower than the sealing protrusion formed at the first separator.

The height of the protrusion formed at the second separator may be equal to or less than the sum of the thicknesses of the first and second separators.

The width of the gasket may be greater than the width of the sealant.

The gasket may be formed by injecting (injection molding) an elastic rubber material, and the sealant may be coated by screen coating.

According to another aspect of the present invention, there is provided a fuel cell stack formed by stacking a plurality of unit cells, the fuel cell stack including: a plurality of unit cells each including a membrane electrode assembly having a subgasket disposed on each side thereof, a pair of gas diffusion layers, an anode separator and a cathode separator, wherein the anode separator and the cathode separator constituting adjacent cells are arranged to face each other and joined together to be integrated with each other, the anode separator may have a protruding sealing protrusion providing sealing; and the cathode separator may have an arch-shaped protrusion protruding in the same direction as the sealing protrusion at a position corresponding to a position where the sealing protrusion is formed.

The gasket may be disposed on a concave surface of the projection opposite to a convex surface of the projection at a position where the projection of the cathode separator is formed, and the sealant may be applied to the convex surface of the sealing projection at a position where the sealing projection of the anode separator is formed.

The sealing protrusion formed at the anode separator may protrude toward the subgasket adjacent to the sealing protrusion and may be sealed by the sealant in close contact with the subgasket; in the region where hydrogen flows, the anode separator and the cathode separator may be joined together at the positions on both sides of the sealing projection by a joint; and the sealing protrusion may have a pair of through-holes through which both sides of the sealing protrusion communicate with each other to allow hydrogen to flow between the anode separator and the subgasket.

The protrusions formed at the cathode separator may protrude in a direction opposite to the adjacent subgaskets and may be sealed by the gaskets being in close contact with the subgaskets; in the region of air flow, the cathode separator and the anode separator may be spaced apart from each other at a position outside the projection around (near) the upstream side of the air flow path with respect to the air flow direction, and the cathode separator and the anode separator may be joined together by a joint point at a position outside the projection around (near) the downstream side of the air flow path with respect to the air flow direction; and the cathode separator may be perforated at a position outside the projection around (near) a downstream side of the air flow path with respect to the air flow direction, thereby forming through holes passing through the first and second surfaces of the cathode separator, thereby allowing the air flowing between the cathode separator and the anode separator to flow between the cathode separator and the subgasket.

The protrusion formed at the cathode separator may protrude in a direction opposite to the adjacent subgasket and may be sealed by the gasket being in tight contact with the subgasket, and in the area where the air flows, the gasket may have a step such that both sides of the gasket communicate with each other through the step, thereby allowing the air to flow between the cathode separator and the subgasket.

The anode separator may be sealed by a sealant in tight contact with the sub-gasket, and the cathode separator may be sealed by a gasket in tight contact with the sub-gasket, and in the region where the coolant flows, the anode separator and the cathode separator may be spaced apart from each other at positions on both sides of a sealing protrusion formed in the region where the coolant flows between the anode separator and the cathode separator, so that the coolant flows between the anode separator and the cathode separator.

According to the present invention, when a pair of separators are joined together to be integrated with each other, a sealing protrusion is applied to one separator, while an arched protrusion and a rubber gasket are applied to the other separator, whereby the stack can have improved airtightness and durability while reducing the production cost.

Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

fig. 1 (prior art) is a view showing the structure of a typical fuel cell stack;

fig. 2 (prior art) is a view showing a unit cell of a fuel cell to which a sub-gasket is applied;

fig. 3 (prior art) is a view showing the configuration of a gasket in a unit cell of a fuel cell to which a sub-gasket is applied;

fig. 4 and 5 are views showing main components of a separator assembly for a fuel cell according to an embodiment of the present invention;

fig. 6 is a view illustrating a region where hydrogen flows in a separator assembly for a fuel cell according to an embodiment of the present invention;

fig. 7 and 8 are views illustrating regions where air flows in a separator assembly for a fuel cell according to an embodiment of the present invention;

fig. 9 is a view showing a region where coolant flows in a separator assembly for a fuel cell according to an embodiment of the invention; and

fig. 10 is a view showing a surface pressure acting on a separator assembly for a fuel cell according to an embodiment of the present invention.

Detailed Description

It is to be understood that the term "vehicle" or "vehicular" or other similar terms as used herein generally includes motor vehicles such as passenger cars including Sports Utility Vehicles (SUVs), buses, trucks, various commercial vehicles; watercraft, including a variety of boats, ships, aircraft, etc., and including hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen powered vehicles, and other alternative fuel vehicles (e.g., fuel from non-petroleum resources). As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, such as a vehicle having both gasoline-powered and electric power.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. Throughout this specification, unless explicitly described to the contrary, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. Also, the terms "unit", "machine", "unit", and "module" described in the specification mean a unit that processes at least one function and operation, and may be implemented by hardware components or component assemblies and combinations thereof.

Furthermore, the control logic of the present invention may be embodied as a non-transitory computer readable medium on a computer readable medium containing executable program instructions for execution by a processor, controller, or the like. Examples of computer readable media include, but are not limited to, ROM, RAM, Compact Disc (CD) -ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer readable medium CAN also be distributed over a network coupled computer systems so that the computer readable medium is stored and executed in a distributed fashion, such as through a telematics server or Controller Area Network (CAN). #

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Exemplary embodiments of the present invention are shown to fully disclose the invention and to assist those of ordinary skill in the art in the best understanding of the invention. Various changes to the following embodiments are possible, and the scope of the present invention is not limited to the following embodiments. The same reference numbers will be used throughout the drawings to refer to the same or like parts.

The fuel cell stack according to the embodiment of the present invention is proposed to improve the shape and the gas-tight structure of the separator while maintaining the stack structure according to the related art shown in fig. 1 and 2, thereby improving the gas-tightness while ensuring the fluidity of the reaction gas and the coolant. Therefore, as shown in fig. 1 and 2, a fuel cell stack according to an embodiment of the present invention includes a plurality of unit cells stacked in series with each other. Each unit cell has: a Membrane Electrode Assembly (MEA)10 having subgaskets 14 disposed on each side thereof; a pair of Gas Diffusion Layers (GDLs) 20; and anode and

cathode separators

30a and 30 b. Therefore, the anode separator 30a constituting one unit cell and the cathode separator 30b constituting an adjacent unit cell are arranged to face each other. In the present embodiment, the anode separator 30a and the cathode separator 30b facing each other are joined together to be integrated with each other, thereby forming a separator assembly.

Fig. 4 and 5 are views showing main components of a separator assembly for a fuel cell according to an embodiment of the present invention. For example, fig. 4 and 5 show the shape and the air-tight structure of the separator improved in the present embodiment. Here, for convenience of explanation, the subgasket 14, the anode separator 200, and the cathode separator 100 are shown in a state of being spaced apart from each other.

As shown in fig. 5, the separator assembly for a fuel cell according to the present embodiment is proposed to minimize deformation of the separator caused by surface pressure while maintaining airtightness in the case where the separator assemblies are stacked and pressed against each other, and preferably includes: a first separator 200 having a protruding sealing boss 210 that provides a seal; a second separator 100 joined to the first separator 200 to be integrated therewith and having an arch protrusion 110 protruding in the same direction as the sealing protrusion 210 at a position corresponding to a position where the sealing protrusion 210 is formed; a spacer 300 provided on a concave surface of the protrusion 110 opposite to a convex surface of the protrusion 110 at a position where the protrusion 110 of the second separator 100 is formed; and a sealant 400 applied to a convex surface of the sealing protrusion 210 at a position where the sealing protrusion 210 of the first separator 200 is formed. Hereinafter, the first separator 200 will be described as an anode separator, and the second separator 100 will be described as a cathode separator.

Further, preferably, the gasket 300 is formed by injecting (injection molding) an elastic rubber material, and the sealant 400 is applied by screen coating.

As described above, the protrusion 110 corresponding to the sealing protrusion 210 provided at the anode separator 200 is provided at the cathode separator 100. This is to prevent a situation in which, if a surface pressure acts on a portion where the sealing protrusion 210 is formed when stacking the fuel cell stack, the cathode separator 100 is deformed toward a space between the cathode separator 100 and the anode separator 200 defined by the sealing protrusion 210, resulting in a decrease in the contact force between the cathode separator 100 and the anode separator 200 and a decrease in the gas tightness of the stack.

For this reason, in the present embodiment, the arch-shaped protrusion 110 is formed at the cathode separator 100 in advance, so that the arch-shaped structure prevents deformation of a portion where the sealing protrusion 210 is formed even if surface pressure is generated on the portion.

Therefore, it is preferable that the protrusion height of the protrusion 110 formed at the cathode separator 100 is lower than the protrusion height of the sealing protrusion 210 formed at the anode separator 200. More excellentPreferably, the height h of the protrusions 110 is equal to or less than the sum of the thicknesses of the anode separator 200 and the cathode separator 100. Further, it is preferable that the width W of the gasket 300_GGreater than the width W of the sealant 400_SIn order to disperse the surface pressure. More preferably, the width W of the shim 300_GGreater than the width W of the sealant 400_SAnd the sum of stacking tolerances. If the width W of the sealant 400_SIs greater than width W of shim 300_GThe width of the sealing protrusion 210 is also increased accordingly. In this case, the rigidity of the sealing protrusion 210 is weak. Therefore, when the fuel cell stack is stacked, the sealing convex portion 210 may be deformed, resulting in a decrease in airtightness.

On the other hand, it is preferable that the above-proposed airtight structure be applied to the region surrounding the MEAs constituting the fuel cell stack and the region surrounding the plurality of inlet manifolds and the plurality of outlet manifolds, so as to ensure the airtightness of these regions.

However, flow paths for flowing reaction gases such as hydrogen and air and a coolant must be ensured between the reaction face where the MEA is located, the inlet manifold, and the outlet manifold.

Accordingly, the separator assembly according to the present invention may change the structure of any one of the sealing protrusion, the protrusion, and the gasket such that a flow path is formed in each region where hydrogen, air, or coolant flows.

Fig. 6 is a view illustrating a region where hydrogen flows in a separator assembly for a fuel cell according to an embodiment of the present invention; fig. 7 and 8 are views illustrating regions where air flows in a separator assembly for a fuel cell according to an embodiment of the present invention; fig. 9 is a view illustrating a region where coolant flows in a separator assembly for a fuel cell according to an embodiment of the present invention. For example, fig. 6 corresponds to a cross-sectional structure taken along line a-a in fig. 2, fig. 7 and 8 correspond to a cross-sectional structure taken along line C-C in fig. 2, and fig. 9 corresponds to a cross-sectional structure taken along line B-B in fig. 2.

First, in the region where hydrogen flows as shown in fig. 6, the sealing protrusion 210 formed at the anode separator 200 protrudes toward the subgasket 14 adjacent thereto, and is sealed by the sealant 400 being in close contact with the subgasket 14. Here, the anode separator 200 and the cathode separator 100 are joined together at positions on both sides of the sealing protrusion 210 by the joining points W1 and W2.

Further, the sealing projection 210 has a pair of communication holes 211, and both sides of the sealing projection 210 communicate with each other through the pair of communication holes 211. Therefore, hydrogen flows between the anode separator 200 and the sub-gasket 14 through the pair of communication holes 211, and the hydrogen is thereby supplied to the reaction surface.

Further, in the area of air flow shown in fig. 7, the protrusion 110 formed at the cathode separator 100 protrudes in the opposite direction to the adjacent subgasket 14 and is sealed by the gasket 300 being in close contact with the subgasket 14. Here, the cathode separator 100 and the anode separator 200 are spaced apart from each other at a position outside the protrusion 110 around the upstream side of the air flow path with respect to the air flow direction, and the cathode separator 100 and the anode separator 200 are joined together at a position outside the protrusion 110 around the downstream side of the air flow path with respect to the air flow direction by a joining point W1.

Further, the cathode separator 100 is perforated at a position outside the protrusion 110 around the downstream side of the air flow path with respect to the air flow direction, thereby forming through holes 111 passing through the first and second surfaces of the cathode separator, thereby allowing the air flowing between the cathode separator 100 and the anode separator 200 to flow between the cathode separator 100 and the subgasket 14. Therefore, at a position outside the protrusion 110 around the upstream side of the air flow path with respect to the air flow direction, the air passes through the through-hole 111 after passing between the cathode separator 100 and the anode separator 200. Thereafter, at a position outside the projection 110 around the downstream side of the air flow path with respect to the air flow direction, air flows between the cathode separator 100 and the subgasket 14, whereby the air is supplied to the reaction surface.

Meanwhile, fig. 8 shows another embodiment of the air flow in the area of the air flow. The protrusion 110 formed at the cathode separator 100 protrudes in a direction opposite to the adjacent subgasket 14 and is sealed by the gasket 300 being in close contact with the subgasket 14. Further, the anode separator 200 and the cathode separator 100 are joined together at the positions on both sides of the sealing protrusion 210 by the joining points W1 and W2.

Here, the gasket 300 disposed between the cathode separator 100 and the subgasket 14 has a step 310 such that both sides of the gasket 300 communicate with each other through the step 310. Thus, air is allowed to flow between cathode separator 100 and subgasket 14, thereby supplying air to the reaction surface.

Meanwhile, in the region where the coolant flows as shown in fig. 9, anode separator 200 is sealed by sealing agent 400 being in close contact with subgasket 14, and cathode separator 100 is sealed by gasket 300 being in close contact with subgasket 14.

Here, the anode separator 200 and the cathode separator 100 are spaced apart from each other at positions formed at both sides of the sealing protrusion 210 in the region where the coolant flows. Thus, coolant is allowed to flow between the anode separator 200 and the cathode separator 100.

On the other hand, fig. 10 is a view showing a surface pressure acting on a separator assembly for a fuel cell according to an embodiment of the present invention. When a fuel cell stack is stacked by employing the separator assembly according to the present invention, it is found that the surface pressure distribution a shows a tendency that the surface pressure increases as going to the center of the sealing convex portion 210 according to the shape of the sealing convex portion 210. Therefore, in order to prevent the cathode separator 100 from being deformed due to the surface pressure formed as described above, the arched protrusion 110 formed at the cathode separator 100 is used.

Although exemplary embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. A separator assembly for a fuel cell, the separator assembly comprising:

a first separator having a protruding sealing protrusion providing a seal;

a second separator joined to and integrated with the first separator and having an arch-shaped protrusion protruding in the same direction as the sealing protrusion at a position corresponding to a position where the sealing protrusion is formed;

a spacer provided on a concave surface of the projection opposite to a convex surface of the projection at a position where the projection of the second separator is formed; and

and a sealant applied to a convex surface of the sealing protrusion at a position where the sealing protrusion of the first separator is formed.

2. The separator assembly of claim 1, wherein the protrusion height of the protrusion formed at the second separator is lower than the protrusion height of the sealing protrusion formed at the first separator.

3. The separator assembly of claim 2, wherein the height of the protrusion formed at the second separator is equal to or less than the sum of the thicknesses of the first separator and the second separator.

4. A separator assembly as claimed in claim 1, in which the width of the gasket is greater than the width of the sealant.

5. A separator assembly as claimed in claim 1, in which the spacer is formed by injection of a resilient rubber material, and

the sealant is applied by screen coating.

6. A fuel cell stack formed by stacking a plurality of unit cells, the fuel cell stack comprising:

a plurality of unit cells each including a membrane electrode assembly having a subgasket disposed on each side thereof, a pair of gas diffusion layers, an anode separator, and a cathode separator,

wherein the anode separator and the cathode separator constituting the adjacent cells are disposed to face each other and joined together to be integrated with each other,

the anode separator has a protruding sealing ledge that provides a seal; and is

The cathode separator has an arch-shaped protrusion protruding in the same direction as the sealing protrusion at a position corresponding to a position where the sealing protrusion is formed.

7. The fuel cell stack according to claim 6, wherein a spacer is provided on a concave surface of the projection opposite to a convex surface of the projection at a position where the projection of the cathode separator is formed, and

at the position where the sealing convex portion of the anode separator is formed, a sealant is applied to a convex surface of the sealing convex portion.

8. The fuel cell stack according to claim 7, wherein the sealing protrusion formed at the anode separator protrudes toward a subgasket adjacent to the sealing protrusion and is sealed by the sealant being in close contact with the subgasket;

the anode separator and the cathode separator are joined together at positions on both sides of the sealing projection by a joint in a region where hydrogen flows; and is

The sealing protrusion has a pair of through-holes through which both sides of the sealing protrusion communicate with each other, thereby allowing hydrogen to flow between the anode separator and the subgasket.

9. The fuel cell stack according to claim 7, wherein the protrusion formed at the cathode separator protrudes in a direction opposite to that of the adjacent subgasket and is sealed by the gasket being in tight contact with the subgasket;

in the region of air flow, the cathode separator and the anode separator are spaced apart from each other at a position outside the projection around the upstream side of the air flow path with respect to the air flow direction, and the cathode separator and the anode separator are joined together at a position outside the projection around the downstream side of the air flow path with respect to the air flow direction by a joining point; and is

The cathode separator is perforated at a position outside the projection around a downstream side of an air flow path with respect to an air flow direction, thereby forming a through hole passing through the first and second surfaces of the cathode separator, thereby allowing air flowing between the cathode separator and the anode separator to flow between the cathode separator and the subgasket.

10. The fuel cell stack according to claim 7, wherein the protrusion formed at the cathode separator protrudes in a direction opposite to that of the adjacent subgasket and is sealed by the gasket being in tight contact with the subgasket, and

in the region where the air flows, the gasket has a step such that both sides of the gasket communicate with each other through the step, thereby allowing the air to flow between the cathode separator and the subgasket.

11. The fuel cell stack of claim 7 wherein the anode separator is sealed by the sealant in intimate contact with the subgasket and the cathode separator is sealed by the gasket in intimate contact with the subgasket, and

in the region where the coolant flows, the anode separator and the cathode separator are spaced apart from each other at positions on both sides of a sealing protrusion formed in the region where the coolant flows between the anode separator and the cathode separator, thereby allowing the coolant to flow between the anode separator and the cathode separator.